The bacterial world of animals

Zoo Atlanta is not just about animals. Indeed, people are not just about people. Recent advances in analyzing genetic samples have broken down the former wall that prevented scientists from really describing the bacterial fauna (“microbiome”) that lives on, in, and in association with all forms of life. We now can calculate the number and diversity of the microbiome in biological samples. Simple moist cotton swabs run across your hand, your inner cheek, and your foot will reveal thousands of types of bacteria, with numbers in the millions. What’s more, those three spots on your body will show that they each have a unique microbiome living there.

The questions one can ask, now, are endless. How similar is your foot to someone else’s? Does that person live in your house, or are they on the other side of the world? How many of those bacteria are harmful, beneficial or benign? Does your microbiome change if you go barefoot all day? Did you get some of your distinct microbiome at birth, from your mother? You get the idea. In a recent project, we joined a long list of collaborators examining zoo (including Zoo Atlanta) and farm animals and compared them to their wild counterparts. Then we asked, what are the effects of a zoological or farm setting on the microbiome in the digestive tracts of mammals?

Many, many fecal samples later, the results were fascinating. It turns out that the answer seems to depend on what type of animal is involved. For example, we found that the microbiome of wild and non-wild cattle (bovids), giraffes, anteaters, and aardvarks are equivalent. The microbiome of other creatures, including canids, primates, and horses (equids), decline in diversity outside the wild. Rhinos, on the other hand, show increased microbioal diversity in zoological settings. The relative abundance of the included microbial forms also differs according to the type of animal, its normal diet type, and whether it is a gut-fermenting species (e.g., the bovids) or not.

This array of differences, varying in different degrees and directions, underscore the real functional importance of an animal’s microbiome. The results also teach us not to generalize across animal types—more microbial diversity is not necessarily better or worse, and original wild-type microbial diversity may not always be necessary, or even best, for an animal to be healthy. We are at the tip of the iceberg on this line of research, but eventually we should be able to add “gut microbiome screen” to samples taken during routine veterinary exams and use that to track individuals’ health and compare to others. Just think of this massive unseen, microscopic zoo on your next visit to Zoo Atlanta!

Joe Mendelson, PhD
Director of Research

Original publication:
McKenzie, V. J., S. Song, F. Delsuc, T. L Prest, A. M. Olivero, T. M. Korpita, A. Alexiev, K. R. Amato, J. L. Metcalf, M. Kowalewski, N. L Avenan, A. Link, T. Di Fiore, A. Sequin-Orlando, C. Feh, L. Orlando, J. R. Mendelson III, J. Sanders, and R. Knight. 2017. The effects of captivity on the mammalian gut microbiome. Integrative and Comparative Biology doi:10.1093/icb/icx090.